1. Field of the Invention
This invention relates to magnetic sheet materials and more particularly to flexible magnetic sheet materials for therapeutic use.
2. Brief Description of the Prior Art
A number of magnetic sheet materials intended for application to the surface of a human or animal body for therapeutic effect have been devised. Mitsuno, U.S. Pat. No. 5,304,111, discloses a flexible planar magnetic sheet material for therapeutic use having areas of alternating magnetic polarity. Mitsuno discloses a pattern wherein generally circular areas of one magnetic polarity are surrounded by a general background of the opposite magnetic polarity. Mitsuno also discloses a pattern of undulating interdigitated areas of alternating magnetic polarity. Baermann, U.S. Pat. No. 4,549,532 discloses a flexible magnetic sheet for therapeutic use made of magnetic particles dispersed in a rubbery matrix and having concentric circles or rectangles of alternating magnetic polarity. In another embodiment, Baermann's magnetic sheet has sectors of alternating polarity.
The therapeutic magnetic materials of the prior art have attempted to provide a pattern of magnetic polarity that does not have a preferential orientation with respect to anatomical structures, e.g., blood vessels, in or close to the skin. Such patterns are intended to insure that the effect of the magnetic field on the anatomical structures in uniform in any direction. However, the known patterns may not provide for such uniform influence in all cases.
Accordingly a need has continued to exist for an improved therapeutic magnetic sheet material having a pattern that provides a highly symmetrical arrangement of magnetic poles.